The fighting came after Ukraine president-elect Petro Poroshenko promised to negotiate an end to the crisis in the east by offering to open talks with Moscow.

Several vehicles full of armed men were seen arriving in the area next to the airport before gunfire began peppering the strongholds.

Trucks of reinforcements followed shortly after. Vladislav Seleznyov, a spokesman for Kiev’s anti-terrorist operation, wrote on his Facebook account the military had given an ultimatum to the armed groups occupying the airport to lay down their arms.

Denis Pushilin, a leader of the separatists, said they had sent men to the airport to help supporters who had been detained.
After claiming victory in Sunday’s vote, Mr Poroshenko said his first step as president will be to visit the Donbass eastern industrial region, where separatists have seized government buildings and declared independence.

‘Peace in the country and peace in the east is my main priority,’ he added. But he had harsh words for the pro-Russia gunmen, comparing them yesterday to ‘Somalian pirates’.

Russia welcomed Mr Poroshenko’s offer of talks, raising hopes that his election will ease tensions between the two countries.